The problem is when the amplifier is switched on, the relay closes for a split second then continues to work as normal as part as the protection circuit, could this be the relay on its way out? as the transistors in the circuit check ok.

Any idea's

Thanks

robbie b

18th January 2013 11:33 AM

protection accuphase E202

when I remember correctly there is an IC u1237 which controls the protectionsystem. After several years this IC sometimes goes bad.
When replacing this IC, also change the relay, after so many years it has burnt contacts.

Goodluck
Rob

reddish75

18th January 2013 11:51 AM

No IC its transistor controlled.

moschfet

18th January 2013 12:34 PM

It is worthwhile anyway to renew all of the switches and relays in such an old amp.

Yes i have it thanks, and all the circuit seems to check out, but i just want to check its just the relay thats at fault as its a major job to remove and replace it.

Just to reitarate the problem the relay fully closes as soon as the amplifier is switched on for a split second.

robbie b

18th January 2013 03:02 PM

Quote:

Originally Posted by reddish75
(Post 3331485)

Yes i have it thanks, and all the circuit seems to check out, but i just want to check its just the relay thats at fault as its a major job to remove and replace it.

Just to reitarate the problem the relay fully closes as soon as the amplifier is switched on for a split second.

my 2 cents
check the capacitors, it seems that at startup the operation voltage is causing to close the relay, afterwards due to perhaps excessive leakage or a defective capacitor, the operating voltage is never reached, thus the relay never closes again.:confused:

reddish75

18th January 2013 03:15 PM

The relay do'es close again as stated in the first post, after the initial 'close' it then opens after a split second then operates as normal i.e after ~4 seconds Q7 turns off and Q8 turns on closing the relay.

Bigred

19th January 2013 12:13 AM

The relay on it's way out? Relay operation doesn't typically decline. Now the actual contacts and such are a different story. I'd say with the proper drive, the relay is either going to energize or it's not. If the relay didn't close with the proper drive then the coil resistance is a miss or open.

Are you overlooking the impedance detect part of the protection circuit? Under normal circumstances the relay WILL close right after powering on. Without the speaker terminals connected to the impedance detect circuit, how would it detect an abnormal load or not? :) Everything being normal, you should be able to hear the low level AC signal during the delay and DC detect period.